Tracks for crawler type machines



July 28, 1959 F. H. DARRAGH, JR 2,897,014

TRACKS FOR CRAWLER TYPE MACHINES I INVENTOR. Frank H.Darragh,Jn

His TTQRNELS July 28,' 1959 x F, H, DARRAGH; JAR l 2,897,014

v TRACkS FOR CRAWLER TYPE MACHINES 5 Sheets-Sheet 2 Filed oct'. 4, 1956m. m w

Frdnk H.Darragh,J|:

-BY I w His ATTORNEYS July 28, 1.959 F. H. D ARRAGH, JR

TRACKS FOR CRAWLER TYPE MACHINES 5 Smeets-sheet s Filed 001,. 4, 1956INVENTOR. Frank H.Darragh,J|:

BY A

YHis ATTORNEYS United States Patent@ TRACKS FOR CRAWLER TYPE MACHINESFrank H. Darragh, Jr., Beaver Falls, Pa., assignor to DarraghMechanisms, Inc., a corporation of Pennsylvania Applicaton October 4,1956, Serial No. 613,873

11 Claims. (Cl. 30S-10) Crawler types machines are old and Well known inthe art and particularly comprise tractors and the like.

There are several objections to tracks presently used for crawler typemachines. Such tracks comprise a large number of parts which are smalland must therefore be made of exceedingly strong materials to withstandheavy loads. The track mechanism is constantly exposed to dirt and otherabrasive material so that lubrication of moving parts is not evenattempted, resulting in excessive wear. The jointed tracks, elongateddue to stretch and wear, soon get out of mesh with the driving sprocketsand are increasingly likely to fly olf, even through greater tension isapplied. Thus conventional crawler machines are currently limited in thelength of their tracks, and even so they must be operated at slowspeeds.

I have heretofore made inventions for tracks for crawler type machineswhich inventions are disclosed in United States Letters Patent 2,308,327and 2,581,365. The present invention is an improvement over my priorinventions and obviates dilhculties encountered therein. l provide atrack unit comprising machine support means, an endless rail connectedto and supporting said support means, said rail having a load bearingportion and a shoe return portion, a plurality of shoes in endlesspivotal connection, each of said shoes having a pair of inner railfollowers and a pair of outer rail followers, and drive means to causemovement of said shoes along the rail. I preferably provide an endlessrail in longitudinally slidable connection with the support member andmeans urging said rail longitudinally forward. I further pref-A erablyprovide circular drive means in contact with the inner rail followersand rail transverse stiffening means. Other details, objects andadvantages of my invention will become more apparent as the followingdetailed description of a present preferred embodiment thereof proceeds.

In the accompanying drawings I have illustrated a present preferredembodiment of my invention in which Figure 1 is a side elevational viewof a crawler type tractor with a track embodying my invention;

Figure 2 is a sectional view of one track unit taken on line II-II ofFigure l;

Figure 3 is a sectional view of a part of one track unit taken on lineIII-lIl of Figure 1;

Figure 4 is an exploded View illustrating one of the shoes; and

Figure 5 is an exploded view illustrating a modified form of the shoeshown in Figure 4 but with certain parts removed.

Referring to the drawings, a crawler type tractor 1 is illustrated inoutline. A crossbar 2 projects from the tractor and serves to support itfrom the track units on either side. A tractor rear axle 3 projects fromthe tractor transmission and further supports the tractor. Achannel-shaped support member 4 is welded to a raised plate 5 which isin turn fastened to crossbar 2 by bolts 6 and clamps 7. It will beunderstood that although only one track unit is shown in the drawings, asimilar Patented July 28, 1959 track unit is provided on the oppositeside of the tractor. A bearing plate 8 is also Welded to the top surfaceof support member 4 and carries in cradle 9a an outboard axle bearing 9in which axle 3 is journaled. A continuous track 10 generally encirclessupport member 4. It is of rectangular cross section throughout, asshown in Figure 2, and may be readily formed from bar stock. Itcomprises a load bearing portion 10a and a shoe return portion 10b. Aload stiffening member 11 comprising a vertical metal plate is weldedalong the load supporting portion 10a of track 10 adjacent the innercorner which is nearest the tractor. A further stiifening plate 12Comprises an extensionof plate member 11. A flat plate 13 is welded tothe top of stifening member 11 with its axis generally parallel to theaxis of load supporting portion 10a. Two spacers 14 are Welded to theupper surface of plate 13 and have bolts 15 threaded into them. Bolts 15project through slotted holes 16 in support member 4. Front and rearspring castings 17 and 18, respectively, are attached to plate 5 and apair of springs 19 is fitted in compression between rear spring casting18 and a saddle 2l) which is slidably mounted in front spring casting17. A push rod 21 is fitted in saddle 20 and bears against a seat 22mounted on member 23 which is welded to stiffening plate 12. Aprojecting guard member 24 may optionally be attached to channel 4. Awheel 25 having a smooth, regular outer circumference is bolted to rearaxle 3.

A transverse stilfening member 51 is bolted at one end to rear springcasting 18 and has its other end welded to the inner edge of track 10.It adds lateral stiffness to the upper portion of track 10. A cover 52of light gauge metal protects springs 19.

A plurality of shoes are mounted in endless rolling relation to track 10in a manner described below in greater detail. Referring now to Figure 4in which one of the shoes is shown in greater detail, each shoe com.-prises side plates 26 and 27 as well as a bottom member 28. Side plates26 are `nearest the tractor and side plates 27 are away from thetractor. Bottom member 28 has a cleat 29 welded to it and is adjacentthe ground when it is in load supporting position. Curved protectivemembers 3i) cooperate with side plates 26 and 27 and bottom member 28 tofurther form a box-like shoe structure. A bolt 31 projects through ahole in side plate 27 and is secured by a nut 32 on the opposite side ofside plate 26. A bushing 33 having two collars 33a and 33h upon it, isplaced over the shank of bolt 31. A spoollike roller 34 having flanges35 at each end is fitted over bushing 33 and is mounted on taperedroller bearings 36. A spacer 37 is also mounted on the shank of bolt 31adjacent side plate 26. Spacer 37 and collar 33a serve to maintainroller 34 in proper transverse relationship to the side plates and tomaintain proper clearance. Collar 33h maintains a distinct space betweenroller 34 and side plate 37 as is best illustrated in Figure 2. A secondflanged roller is mounted on each shoe in similar fashion with likeparts being given like numbers.

ln a similar manner, a pair of inner rail followers 38 is provided foreach shoe. Each follower comprises a roller 39 which is journaled uponshaft 40 on a needle bearing. The free end of shaft 40 has a threadedportion which projects through one `of the holes 41 in side plate 27. Alink 42 is placed upon each shaft 40 after which `a jam nut 43 isthreaded onto the end portion. Shaft 40 is then mounted in hole 41 and anut 44 is threaded on and drawn tight.

Referring to Figure 4 it will be seen that the link 42 extends betweenshafts 40 of adjacent shoes. The roller on the adjacent shoe in Figure 4being designated 39a; It will be observed that vonly the roller andshaft assocated with the -adjacent shoe are shown and that no 3 otherportion of the adjacent shoe is illustrated. Studs 45 are welded to sideplate 26 in line with holes 40 and receive links 46 which are of thesame length as links 42. Links 46 connect to adjacent shoes in likemanner jto links 42. VThey `are secured in place by lock nuts 47.

In Figure 5 I have shown a modified form of the shoe illustrated inFigure 4. Like members in Figure 5 have been given like numbers to thoseshown in Figure 4. It will be noted that in place of round holes 41elongated and tapered slots 48 are provided to receive tapered blocks 49of somewhat shorter length. Flat faces 50 have been ground upon thethreaded portions of shaft 40. Each stop 49 has corresponding hatsections to receive and engage the at portion of shaft 40. When nuts 44are drawn tight upon the threaded ends of each shaft 40, the shoulder atthe end of ats 50 will be drawn against blocks 49. This will leaveproper clearance for full swivel movement of link 42. Nut 44 will spanslot 48 and, when properly adjusted will allow movement of block 49lengthwise of the slot. In some instances the blocks 49 may be omittedland bolts 40 with their associated flat sections can be fitted directlyto slots 48.

It will be noted that the distance between the outer rollers 34 in eachshoe is greater than the distance between lthe inner rollers 38. Theobjective is to permit the shoes to roll around the periphery of trackwith a minimum of slack and clearance. When the shoes are on the atportion of track 10, the ideal positions of the inner and outer rollersis on a perpendicular to the axis of track 10. When the shoes are on thecurved portions of track 10, the ideal positions of the inner and outerrollers will again be on a perpendicular to track 10, which will in thisinstance be a radius of the circle which the curved portion of the trackdescribes. It will be apparent that in this condition -a line throughthe centers of rotation of the rollers will be at an angle to aperpendicular through the shoe. A minimum variation is obtained byplacing the inner and outer rollers in a position midway between the twopositions for ideal operation as above described. This condition isobtained when the angle of a line between the rollers and aperpendicular to the shoe is one-fourth of the radial angle formed bythe centers of the two inner rollers on one shoe and the center of thecircle described by the curved portion of track 10.

The shoes are assembled on track 10 by positioning them with the outerrollers 34 already installed in the shoes. The inner rollers 39 are thenput into position and links 42 and 46 are installed. When all of theshoes have 'thus been placed in position they Will be formed in anendless procession around track 10.

In operation power is applied to the rear axle 3 of tractor 1 causingthe axle to rotate. Springs 19 urge track 10 in a forwardly directionand cause inner rollers 39 to be pinched between track 10 and wheel 25.The frictional force between inner rollers 39 and wheel 25 will causerotation of the inner rollers, causing them to VrOll along the innerface of track 10. The shoes will be thus pulled endlessly around track10 and the inner rollers will be continuously rolled around 4the innerportion of track 10, links 42 and 46 serving to maintain the endlessrelationship of the shoes. Outer rollers cooperate with inner rollers 39and track 10 to limit movement of the shoes along track 10. Flanges 35on rollers 34 overlap the sides of track 10 and prevent the shoes fromdrifting to either side. The flanges `are deep enough to hold track 10under all conditions. If the draw bar load upon the tractor isincreased, the added load will jam wheel 25 harder against the insiderollers 3S, thus increasing the frictional force for driving.

Experiments have shown that the frictional force, even with moderatepressure by springs 19, is suicient to enable a standard crawler tractorequipped with the tracks as shown to perform Work equal to that of anidentical machine equipped with conventional tracks, which can be spunagainst the ground. The shoes of my machine, being held rigid andmotionless while in contact with the ground are capable of carryinglarger cleats. They do not slip under the same conditions and hencedeliver more thrust. Springs v19 provide adequate pressure to avoidslippage when the tractor is in reverse.

Guard 24 may be optionally installed to prevent pinching objects betweenthe shoes as they roll onto the lower portion of track 10. It may, forexample, be desired to install such a guard where the tractor is beingused to climb over railroad tracks and the like.

From the foregoing it will be seen that I have invented a new and usefulmechanism which is readily constructed, is durable, and has a minimum ofparts. It is equally operable in either direction. Springs 19 provideadequate force to permit reverse operation. The track and rollers areself-cleaning to ythe greatest possible degree and are constructed ofthe simplest possible components; they will not foul when the tractor isoperated in reverse. It will be seen that the invention makes possiblecrawler vehicles of sizes, speeds and capacities heretofore thoughtimpossible.

Although I have illustrated a present preferred embodiment ofmycinvention, it is tobe understood that I do not limit myself theretoand that my invention may be otherwise variously practiced within thescope of the following claims.

I claim:

l. A track unit for a crawler type machine comprising machine supportmeans, a single endless rail `connected to and supporting said supportmember, Said rail having a load-bearing portion and a shoe returnportion, a plurality of spaced apart shoes mounted on said rail, each ofsaid shoes having inner rail followers on a pair of axes and outer railfollowers, on a pair of axes link means pivotally connecting adjacentshoes, and drive means t0 cause movement of said shoes along said rail.

2. A track unit for a crawler type machine comprising a single endlessrail having a load-bearing portion and a shoe return portion, aplurality of spaced apart shoes mounted on said rail in rolling contactwith the rail, link means pivotally connecting adjacent shoes to form anendless track, a pair of longitudinally spaced inner rail rollers oneach shoe, a pair of longitudinally spaced outer rail rollers on eachshoe, and shoe drive means in driving connection with the shoes.

3. A track unit for a crawler type machine comprising a machine supportmember, an endless rail in longitudinally slidable connection with saidsupport member and having a load-bearing portion and a shoe returnportion, means urging said rail longitudinally forward, a plurality ofspaced apart shoes and intermediate link means in endless, pivotalconnection, each of said shoes having inner rotary rail followers on apair of axes and outer rotary rail followers on a pair of axespositioned for rolling contact with said rail, and drive means infrictional contact with said inner rotary rail followers adjacent a partof said rail.

4. A track unit for a crawler type machine comprising a machine supportmember, an endless rail in longitudinally slidable connection with saidsupport member and having a load-bearing portion and a shoe returnportion, means urging movement of said rail longitudinally, a pluralityof spaced apart shoes and intermediate link means in endless, pivotalconnection, each of Said shOeS having inner rotary rail followers on apair of axes and outer rotary rail followers on a pair of axespositioned for rolling contact with said rail, rotatable drive meansabutting the inner rotary rail followers adjacent a portion of the railand opposing urging of longitudinal move ment of the rail.

5. A track unit for a crawler type machine comprising a machine supportmember, an endless rail in longitudinally slidable relation thereto,said rail comprising a pair of substantially parallel horizontalportions and semicircular portions therebetween, means urginglongitudinal movement of said rail, a plurality of spaced apart shoeseach having inner rail rollers on a pair of axes and outer rail rollerson a pair of axes in rolling contact with the rail, means linking saidshoes endlessly and pivotally, and circular drive means in frictionalcontact with the inside rollers in contact with one of saidsemi-circular portions, said drive means opposing said urging means.

6. A track unit for a crawler type machine comprising a machine supportmember, an endless rail in longitudinally slidable relation thereto,said rail comprising a pair of substantially parallel horizontalportions and semi-circular portions therebetween, means urginglongitudinal movement of said rail, a plurality of shoes each havinginner rail rollers on a pair of axes and outer rail rollers on a pair ofaxes in rolling contact with the rail, means linking said shoesendlessly and pivotally, circular drive means in frictional contact withthe inside rollers in contact with one of said semi-circular portions,and said drive means opposing said urging means, and rail transversestiifening means.

7. A track unit for a crawler type machine comprising a machine supportmember, an endless rail in longitudinally slidable relation thereto,said rail comprising a pair of substantially parallel horizontalportions and semicircular portions therebetween, means urginglongitudinal movement of said rail, a plurality of shoes in rollingcontact with the rail, a pair of longitudinally spaced inner railrollers on each said shoe, a pair of outer rail rollers having a greaterlongitudinal spacing than the inner rail rollers, means linking saidshoes endlessly and pivotally, circular drive means in frictionalcontact with said inner rollers in contact with one of saidsemi-circular portions and opposing longitudinal urging by said urgingmeans.

8. A track unit for a crawler type machine comprising a support member,an endless rail in longitudinally slidable relation thereto and having aload-bearing portion and a shoe return portion, means urging movement ofsaid rail longitudinally, a plurality of discrete spaced apart shoes inrolling contact with said rail, said shoes having inner rail rollers ona pair of axes and outer rail rollers on a pair of axes and contiguousend, side and load-carrying portions, link means endlessly connectingthe shoes by pivotal connection at the inner axes, and circular drivemeans in frictional contact with only a portion of the inner rollers atany given time and opposing said means urging longitudinal movement ofthe rail.

9. A track unit for a crawler type machine comprising a single endlessrail of uniform rectilinear cross section having a shoe load-bearingportion and a shoe return portion, a plurality of spaced apart shoes inrolling contact with the rail, longitudinally spaced inner rail rollerson each shoe on a pair of axes, outer rail rollers on each shoe on apair of axes, the rollers of one of said pairs being anged, and shoedrive means in driving connection with the shoes, and link meansextending between the inner pivotal axes of adjacent shoes.

10. A track unit for a crawler type machine comprising a machine supportmember, a single endless rail of uniform rectilinear cross sectionhaving a load-bearing portion and a shoe return portion, a plurality ofspaced apart shoes in rolling Contact with the rail, said shoes beingendlessly and pivotally connected, inner rail rollers 0n a pair oflongitudinally spaced axes on each shoe, flanged outer rail rollers on apair of longitudinally spaced axes on each shoe, shoe drive means indriving connection with the shoes, and means urging the rail and some ofsaid shoes longitudinally against the drive means.

l1. A track unit for a crawler type machine comprising a machine supportmember, a single endless rail of rectilinear cross section inlongitudinal movable connection therewith, said rail having aload-bearing portion and a shoe return portion, a plurality of shoes inrolling contact with the rail, said shoes being endlessly and pivotallyconnected, inner rail rollers on a pair of longitudinally spaced axes oneach shoe, anged outer rail rollers on a pair of axes spaced a greaterdistance apart than the inner roller axes, circular drive means infrictional contact with some of the inner rollers, and means urging saidrollers against said drive means.

References Cited in the le of this patent UNITED STATES PATENTS1,839,766 Tourneau Jan. 5, 1932 2,581,365 Darragh Ian. 8, 1952 FOREIGNPATENTS 10,404 Great Britain May 27, 1895 648,008 Great Britain Dec. 28,1950 UNITED STATES PATENT OFFICE CERTIFICATE 0E CORRECTION Patent No..2,897,014 July 28, 1959 Frank H.. Darragh, .In

/N It is hereb certified that error appears in the -printedspecification of the above numbered patent requiring correction andthatl the said Letters Patent should read as corrected below.

Column l, line4 l5, for "types" read type column 4, line 36,

for "followers, on a pair of axes" read followers on a pair of axes,column 6, line 42, list o' references cited, under UNITED STATESPATENTS, for "Dari-sgh" read Darragh, Jr, --0

Signed and sealed this 22nd day of December 1959.,

(SEAL) Attest:

KAEL H. AXLTNE ROBERT C. WATSON Attesting Ofcer Commissioner Of Patents

